The perfluorotriazine polymers to which the present invention relates are, as a general class, known materials. See U.S. Pat. No. 4,242,498 issued Dec. 30, 1980 to Rosser, et al. These materials are tough, heat and chemical-resistant elastomers. These advanced properties allow their advantageous use in extreme environments and applications--for example as fuel tank sealants, O-rings, wire enamels, pneumatic ducts and edge close-outs in aircraft.
U.S. Pat. No. 4,242,498 discloses a 4-step preparation procedure for these elastomers. This procedure consists of (1) forming a poly(imidoylamidine) by the reaction under reflux conditions of anhydrous ammonia with certain perfluorinated alkyl or alkylether dinitriles; (2) forming a linear polytriazine by cyclizing the imidoylamidine linkages by reaction with certain perfluorinated alkyl or alkylether acid anhydrides or halides; (3) extending the linear polytriazine chain by further refluxing in anhydrous ammonia; and (4) heating to cyclize the new imidoylamidine linkages and thereby crosslink the polymer.
While this earlier process and the products it produced were good useful advances, they did pose shortcomings. For one, with this process, it was difficult to control or reproduce the molecular size of the polymer product. Moreover, the resulting polymer at times manifested some degree of hydrolytic instability.
Other patents that are of general interest in showing various other similar procedures for producing triazine elastomers of the general type described above include:
U.S. Pat. No. 3,347,901 issued on Oct. 17, 1967 to Fritz, et al;
U.S. Pat. No. 3,250,808 issued on May 10, 1966 to Moore, et al;
U.S. Pat. No. 3,450,646 issued on June 17, 1969 to Annand, et al;
U.S. Pat. No. 3,531,496 issued on Sept. 29, 1970 to Annand, et al;
U.S. Pat. No. 3,637,630 issued on Jan. 25, 1972 to Dorfman, et al;
U.S. Pat. No. 4,234,715 issued on Nov. 18, 1980 to Rosser, et al;
U.S. Pat. No. 4,245,085 issued on Jan. 13, 1981 to Rosser, et al; and
U.S. Pat. No. 4,273,918 issued on June 16, 1981 to Rosser, et al.